SU1755070A1 - Apparatus for temperature measuring and checking - Google Patents

Abstract

Usage: instrumentation, multichannel temperature meters in process controllers. The essence of the invention: the device contains 1 current source (1), N primary measuring converters (2.1 ... 2 N), 1 switch (3), 1 analog-to-digital converter (4), 1 resistor (5), 1 computing unit ( 6), 1 registration and control unit (7), 1 common bus (8). 1-21-3-4- 6-3-5-8, 6-7. 1 il.

Description

The invention relates to multichannel devices for measuring temperature and its associated physical quantities and can be used in controllers of various technological processes.

A device for measuring temperature is known, comprising a first and second current source, an inverter, an adder, a three-core cable, two thermal resistances and a switch.

The disadvantages of this device are low accuracy due to the presence of two current sources, the output currents of which must be maintained with high accuracy, determined by the accuracy of the device itself, as well as the impossibility of organizing multi-channel measurement mode and temperature control.

The closest in technical essence to the present invention is an information-measuring system for temperature measurement, containing transducers and test generators, a switch, the output of which is connected to the input of the ADC, the output of which is connected to the input of the calculator, the control input which is connected to the inputs of the controller / G of the switch and the ADC, and the information output - to the inputs of the display unit and the registration and control units 1.

The disadvantage of the device is low measurement accuracy, due to the presence of n power sources of measuring transducers

The purpose of the invention is to improve the accuracy of temperature measurement,.

The goal is achieved by the fact that a device for measuring and controlling temperature, containing a current source, n primary measuring transducers connected by outputs to the corresponding n inputs of a switch, is an analog-to-digital converter whose output is connected to the input

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a computational unit connected by the information output to the information input of the registration and control unit, and the control outputs to the control inputs of the switch and the analog-digital converter are entered a resistor and a common bus with which the resistor is connected to one output and its other output is connected to the output the switch, which is also connected to the reference input of the analog-digital converter, the output of the current source is connected to the information input of the analog-digital converter with the (n + 1) -th input of the switch and to the inputs transducers.

The drawing shows a diagram of the device.

The device contains a current source 1, the output of which is connected through primary measuring converters 2.1 ... 2.P with the corresponding n inputs of the switch 3 and directly with the information input of the analog-digital converter (ADC) 4 and (n + 1) -th input of the switch 3 whose output is connected to the reference input of the ADC 4. The output of the ADC 4 is connected to the input of the computing unit 6, the information output of which is connected to the input of the recording and control unit 7. The control outputs of the computing unit 6 are connected to the corresponding control inputs of the switch 3 and the A / D converter 4, and a resistor 5 is connected between the output of the switch 3 and the common bus 8. (

The device works as follows.

The measured temperature field is transformed by every 1st of the converters 2.1 ... 2.1 .., 2, n, respectively, into the resistance of the Poison |, described by the linear relation

Rd | K, T, (1)

where KI is the temperature coefficient of the primary converter 2.I, which is determined for each primary converter during installation and adjustment and is recorded in the memory of block 6;

T is the temperature.

In this case, the information input of the ADC 4 receives the voltage Ui

Ui 1 (+ RK + Ro), (2)

where RK is the internal resistance of each of the i channels of the switch 3;

Ro - Resistor resistance 5.1 - current source 1 current.

The reference input Do is supplied to the reference input of the ADC 4

U0 l- Ro. (3)

The computing unit 6 alternately connects each of the n + 1 channels of the switch 3, selects the next value of the output current of the ADC 3 - Zi, described by the ratio

Zi Ui / Uo - (+ RK + Ro) / R0, (4)

5 a for the (n + 1) -ro channel of the switch connected directly to the output of the current source 1 is Z (n + 1) (Pk + Ro) / Ro. Then the computation unit b generates the output code Xi:

0 Xi 2i-Z (n + 1) Ki -T. (5)

proportional to the temperature measured by the corresponding converter 2.1 in the 1st cycle along the nth inclusive. In the (n + 1) th cycle, an alternate value of Z (n + 1) is written to the memory of the computing unit b.

The code Xi enters the recording and control unit 7, where the measured temperature is recorded. Thus obtained

0, the results of temperature measurements are free from errors associated with the instability of the current of source 1, the dependence of the resistance of the channels of the switch 3 on the temperature and the supply voltage, the variation of its magnitude in the various microcircuits of the switch.

The choice of the desired temperature measurement channel can be made according to the program recorded in constant

0 a storage device included in the registration and control unit 7, which can be implemented on the basis of a single-crystal microcomputer of the 1820 series or another microprocessor complex.

As a specific example of the device, the series 573 ROM, switch KR590KN6, ADC K572PV1 can be used. Block 7 registration and management

0 may contain a K1820ID1 decoder, an IL Ts-4 / 7M indicator, a control panel and output actuators that provide communication capabilities with an object, whose temperature characteristics are examined using the device. As a primary transducer, any resistor temperature sensors can be used, the type and rating of which is determined depending on the range of measured temperatures.

Claims (1)

Apparatus of the Invention A device for measuring and controlling temperature, comprising a current source, 5 primary transducers connected by outputs to the corresponding n inputs of the switch; an analog-to-digital converter whose output is connected to the input of the computer of the block connected by information the output to the information input of the registration and control unit, and the control inputs to the control inputs of the switch-digital converter, characterized in that, in order to improve the temperature measurement accuracy, a resistor and a common bus with which the resistor is connected are introduced into it one output, and its other output is connected to the switch output, which is also connected to the reference input of the analog-digital converter, the output of the current source is connected to the information input of the analog-digital converter, with the (n + 1) -th input of the switch and the inputs of the primary measuring converters.